Proof-Carrying Smart Contracts

Thomas D. Dickerson, Paul Gazzillo, Maurice Herlihy, Vikram Saraph, Eric Koskinen

Abstract: We propose a way to reconcile the apparent contradiction between the immutability of idealized smart contracts and the real-world need to update contracts to fix bugs and oversights. Our proposal is to raise the contract’s level of abstraction to guarantee a specification $$\varphi $$ instead of a particular implementation of that specification. A combination of proof-carrying code and proof-aware consensus allows contract implementations to be updated as needed, but so as to guarantee that $$\varphi $$ cannot be violated by any future upgrade. We propose proof-carrying smart contracts (PCSCs), aiming to put formal correctness proofs of smart contracts on the chain. Proofs of correctness for a contract can be checked by validators, who can enforce the restriction that no update can violate $$\varphi $$ . We discuss some architectural and formal challenges, and include an example of how our approach could address the well-known vulnerabilities in the ERC20 token standard.